Glioblastoma are aggressive and invasive brain tumors that generally lead to death within a year of diagnosis. No cure is available, and current treatments prolong life by only a few months. In the current application, we propose to study the potential use of vesicular stomatitis virus (VSV) to selectively infect and kill these brain tumors. We have developed recombinant VSVs that selectively infect human glioblastoma and not control cells in vitro, and target glioblastoma cells transplanted into the mouse brain. As these viruses are replication-competent, after killing the first round of glioblastoma, progeny viruses are released which cytolytically infect more glioblastoma cells. Experiments are based on in vitro use of human and mouse glioblastoma and control cells, and on human or mouse tumor cells transplanted into the mouse brain. Four sets of experiments are planned. In the first set of experiments, recombinant VSVs will be used to test the hypothesis that enhancing the cellular interferon response or slowing replication will selectively protect normal, but not brain tumor, cells. VSVs that selectively infect glioblastoma will then be used with in vivo experiments in which human glioblastoma cells that express a red reporter gene are transplanted into the brains of SCID mice, or red mouse glioblastoma is transplanted into the normal immunocompetent mouse brain. VSV will be administered either directly into the brain tumor, or by systemic injection into the tail vein to test the hypothesis that the virus will selectively infect and kill the glioblastoma cells within the brain with little spread to the normal brain tissue. To increase the safety profile related to oncolytic viruses in the brain, a third set of in vitro and in vivo experiments will test several antiviral drugs (interferons, ribavirin, aspirin, polylC, IL-12) that have been reported to be effective in controlling viral infections to determine which is the most efficacious in blocking possible VSV infections of normal brain. The hypothesis that peripheral VSV immunization will attenuate a later cerebral infection by recombinant VSV will be tested. A final set of experiments will test the hypothesis that recombinant VSV will show no, or relatively little infection and replication in non-tumor slices of the human brain in vitro. The primary goal of these studies is to test the efficacy and safety of variant oncolytic VSVs as the first step as a potential treatment for currently incurable human brain tumors.